Former House Speaker Newt Gingrich on Thursday "strongly" endorsed John McCain — calling him "a national treasure" — as he squares off in a blistering effort to represent Arizona for the sixth time in the Senate.

"I strongly endorse Senator John McCain," Gingrich, the former Georgia congressman, said in a video released by the McCain campaign. "A genuine American hero, a man who has endured a great deal for his country — and a man who I work with and watch him provide leadership as chairman of the Armed Services Committee.

"I know how hard John works for veterans, for the military, for our national security — and I know that John McCain is a national treasure.

"Somebody who’s making a real difference, a man of great courage, who is a patriot, who serves his country without fear," he added. "I hope you do everything you can to make sure Senator John McCain continues to work in Washington on your behalf, and on behalf of all Americans."

The senator, a Vietnam War Navy veteran, slammed Trump this week for his attack of the parents of a Muslim Army captain who died in Iraq in 2004.

McCain is facing a tough re-election challenge from former Arizona state Sen. Kelli Ward. The winner of the Aug 30 Republican primary faces Democratic Rep. Ann Kirkpatrick in November.

"I am honored to receive the endorsement of Speaker Gingrich, a long-time friend and leader in the Republican Party," McCain said. "Throughout his career, Newt has been a strong voice for conservative principles.

Former House Speaker Newt Gingrich on Thursday "strongly" endorsed John McCain — calling him "a national treasure" — as he squares off in a blistering effort to represent Arizona for the sixth time in the Senate.